A strand coating system is configured to apply a hot melt adhesive onto one or more strands of material. Such a system is often used to coat elasticated strands of material with a hot melt adhesive for use in the construction of disposable hygiene products such as diapers. The coated elastic strands may be adhered to an underlying substrate with the hot melt adhesive to form, for example, leg elastics, cuff elastics or waist elastics of the disposable hygiene product.
The strand coating system includes a nozzle for discharging the hot melt adhesive onto the one or more elasticated strands of material. The nozzle assembly may be a contact applicator assembly for applying the adhesive directly onto the strands or a non-contact applicator assembly, where the adhesive is discharged over an air gap onto the strands. The nozzle includes an orifice through which the hot melt adhesive may be discharged. In one strand coating system, the flow of hot melt adhesive through the nozzle may be metered to control a coating weight of the hot melt adhesive on the strand of material.
In some applications, it may be desirable to vary a coating weight of the hot melt adhesive along a length of the strand of material. Such varied coating weights may be realized in a number of different ways. For example, the strand of material may be passed through a nozzle multiple times. For instance, a first pass through a nozzle may allow for a base coating on the strand, and a second or subsequent pass through the nozzle may allow for intermittent application of the hot melt adhesive to selectively add weight to the strand. However, such a process is time consuming and labor intensive.
Another system for varying the coating weight of a hot melt adhesive applied to the strand of material involves using two spaced apart nozzles arranged along a direction of travel of the strand of material. A first nozzle may apply a base coating of hot melt adhesive to the strand and a second nozzle may be controlled to add weight to the strand. However, such a system requires additional equipment (e.g., multiple nozzles) and may occupy a large area in a manufacturing assembly due to the additional equipment.
Still another system for varying a coating weight of a hot melt adhesive on a strand of material is described in U.S. Pat. Appl. Pub. No. 2017/0128968 to Adams et al., which is incorporated herein by reference in its entirety. In a non-contact application, Adams et al. uses two separate nozzles, independently operated, to apply the hot melt adhesive material to an elasticated strand. For example, one nozzle applies a base layer of hot melt adhesive to a plurality of elasticated strands, and a second, distinct nozzle is operated to apply a second layer of hot melt adhesive to the strands, thereby selectively adding weight to the strands. However, as described above, the use of multiple nozzles increases equipment and associated costs, maintenance, space and the like. In addition, by using a single nozzle and single orifice to apply the hot melt adhesive to multiple strands, overspray (discharged hot melt not received on a strand) may become an issue, which can lead to an inefficient coating process and increased material costs.
In a contact application, Adams et al. provides a nozzle having multiple discharge orifices arranged in a direction along a length of the elasticated strand. Flow of hot melt adhesive may be controlled through each discharge orifice as either on or off to control a coating weight of hot melt adhesive applied on the elasticated strand. That is, a coating weight of the hot melt adhesive may be controlled by allowing or preventing hot melt adhesive to be discharged from different discharge orifices. However, manufacture of such a nozzle requires significant machining, which may be time consuming and costly.
Accordingly, it is desirable to provide a fluid application device in a strand coating system capable of discharging varying volumes of a material from a single orifice of a nozzle.